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  • What is the maximum data size you can store in a PHP session?
    What is the maximum data size you can store in a PHP session?
    PHPsessionshavenostrictsizelimit,butstoringlargedatacancauseperformanceandmemoryissues.1.Defaultfile-basedstorageslowsdownwithlargesessiondataduetolocking.2.Largesessionsincreasememoryusageandriskhittingmemorylimits.3.UsescalablehandlerslikeRedisforh
    PHP Tutorial . Backend Development 542 2025-07-12 01:49:40
  • mysql table lock vs row lock
    mysql table lock vs row lock
    Table locks are suitable for low-concurrency, batch operation or maintenance scenarios. For example, when using the MyISAM engine, performing DDL operations or full-table scans, their overhead is small but their concurrency is poor. Row locks are suitable for high-concurrency write scenarios. They are supported by the InnoDB engine. Fine-grained locks are realized through index hits to improve concurrency but may cause deadlocks. When choosing, according to business needs, use InnoDB row locks with more writes and reads, and use MyISAM table locks with less data or mainly reads, and ensure that querying and indexing can avoid lock upgrades.
    Mysql Tutorial . Database 278 2025-07-12 01:48:41
  • What is the theme-color meta tag?
    What is the theme-color meta tag?
    Theme color meta tags are used to control the display color of the browser address bar or task switcher on mobile devices, improving brand consistency and user experience. It is set by adding to the HTML header, so that the browser UI coordinates with the website theme color, especially when using bookmarks or "Add to Home Screen" on Android devices. Its functions include: 1. Improve visual consistency; 2. Strengthen brand recognition; 3. Improve PWA experience. Best practices include: matching website design, testing on real devices, and adapting to the depth and pattern.
    HTML Tutorial . Web Front-end 325 2025-07-12 01:48:22
  • How to debug PHP session problems?
    How to debug PHP session problems?
    The key to solving PHP session problems is to check the call order, configuration, and data flow. 1. Make sure that each page using session calls session_start() correctly before output to avoid spaces, BOM headers or early output content; 2. Check whether the $_SESSION data is repeatedly initialized, unset or overwritten, and confirm the data process through var_dump or log; 3. Check the session.cookie-related configuration to ensure that the cookies are correctly passed, and troubleshoot the browser interception or domain name setting; 4. Check the server error log and enable the PHP error prompt to confirm that the session storage path can be written or extended configuration is correct, and gradually check common omissions are located
    PHP Tutorial . Backend Development 523 2025-07-12 01:47:01
  • What is the purpose of PHP Namespaces?
    What is the purpose of PHP Namespaces?
    PHPnamespacespreventnamingconflictsandorganizecode.Theyallowmultiplefunctions,classes,orconstantswiththesamenametocoexistbygroupingthemintodifferentnamespaces,suchasApp\Utilities\sendEmail()andThirdParty\Email\sendEmail().1.Namespacesfunctionlikefold
    PHP Tutorial . Backend Development 353 2025-07-12 01:41:41
  • PHP check if a string contains a specific word
    PHP check if a string contains a specific word
    In PHP, determine whether a string contains a specific word, the strpos() function is preferred to check whether the keyword exists. This method is efficient but case-sensitive; if it is necessary to be case-insensitive, the strpos() function can be used; to ensure that the complete word is precisely matched, a regular expression should be used to process special characters with \b word boundaries and preg_quote(); for multi-word judgment or complex scenarios, strpos() can be called continuously, logical conditions, or traverse keyword arrays can be traversed to match.
    PHP Tutorial . Backend Development 887 2025-07-12 01:38:50
  • Using CSS backdrop-filter for unique effects
    Using CSS backdrop-filter for unique effects
    Backdrop-filter can enhance the hierarchy of web pages through blur and other effects, and is suitable for pop-up windows, cards and other components. 1. Use blur to achieve the effect of frosted glass, such as .modal{backdrop-filter:blur(10px); background-color:rgba(255,255,255,0.6);}, and it is recommended to add the -webkit-prefix to improve compatibility; 2. Combining multiple filter functions such as brightness, contrast, etc. can create a richer visual style, but pay attention to the order affecting the effect; 3. Pay attention to the impact of performance consumption, browser compatibility and hierarchy structure on display effect, and adopt a downgrade solution to ensure the page
    CSS Tutorial . Web Front-end 449 2025-07-12 01:37:00
  • mysql composite index example
    mysql composite index example
    MySQL composite index follows the principle of leftmost prefix, and the query condition must include the leftmost column of the index before it can hit the index. 1. The index structure is organized in the order of definition, such as (name, age, city) first sorted by name, and then subdivided in sequence; 2. The hit condition includes continuous combinations starting with the leftmost column, such as WHEREname=... or WHEREname=...ANDage=...; 3. If the leftmost column is not included, it cannot be hit if only age or city is used; 4. When creating, the high-divided and commonly used query fields should be placed in front of it, and redundancy and excessive indexing should be avoided; 5. The use of functions, OR without index support, and fuzzy matching at the beginning of % will cause the index to fail.
    Mysql Tutorial . Database 611 2025-07-12 01:36:01
  • What is the difference between input type='submit' and ?
    What is the difference between input type='submit' and ?
    It is used to submit a form, and the form submission behavior will be automatically triggered when clicked; it is a normal button, and functions need to be defined through JavaScript. 1. The submit type sends data to the server by default in the form, and the submission function can be realized without additional code; 2. The button type has no default behavior and is usually used for front-end interactions such as pop-ups, verification, etc.; 3. Using submit may cause page jumps or refreshes, while buttons are more suitable for executing scripts to avoid unexpected submissions; 4. In framework development, the purpose of the two should be clearly distinguished to reduce debugging costs. Choosing the correct button type can help improve development efficiency and user experience.
    HTML Tutorial . Web Front-end 619 2025-07-12 01:31:01
  • mysql create table syntax
    mysql create table syntax
    The key to creating a MySQL table is to master the basic syntax and common options of CREATETABLE statements. 1. The basic syntax requires specifying field names, data types and constraints, such as NOTNULL, PRIMARYKEY, AUTO_INCREMENT; 2. Common field types include INT, VARCHAR(n), TEXT, DATE, DATETIME, TIMESTAMP and DECIMAL(m,d), which should be selected according to actual needs to optimize storage and performance; 3. Constraints include NOTNULL, UNIQUE, DEFAULT, PRIMARYKEY and FOREIGNKEY. When using foreign keys, the two tables must be engines that support foreign keys (such as
    Mysql Tutorial . Database 633 2025-07-12 01:27:51
  • What is the difference between an HTML element and an HTML tag?
    What is the difference between an HTML element and an HTML tag?
    The difference between HTML elements and HTML tags is: 1. HTML tags are syntax structures in the code, used to define elements, such as and; 2. HTML elements are objects generated by the browser after parsing the tag, including tags, contents and attributes. Tags are text characters used when writing HTML, while elements are actual objects formed when the browser builds a document structure (DOM) and interact with elements during JavaScript operations or CSS-style applications. Understanding this difference helps avoid confusion in debugging and technical discussions.
    HTML Tutorial . Web Front-end 464 2025-07-12 01:27:11
  • What is the target='_blank' attribute in HTML and when to use it?
    What is the target='_blank' attribute in HTML and when to use it?
    When using target="_blank" you should use target="_blank" to stay on the current page, such as jumping to external websites, opening non-web content, or avoiding interruption of the process; precautions include adding rel="noopener" to prevent security vulnerabilities and avoiding abuse to affect navigation and accessibility; misuse scenarios include internal links to open new pages, lack of security attributes, and multi-label explosions; alternatives can be used to pop-up windows, dynamic loading or explicitly prompting users.
    HTML Tutorial . Web Front-end 456 2025-07-12 01:26:42
  • What is the http-equiv attribute in a meta tag used for?
    What is the http-equiv attribute in a meta tag used for?
    Thehttp-equivattributeinatagsimulatesHTTPresponseheaderstocontrolbrowserbehaviorwhenserveraccessisunavailable.1.ItcansetcharacterencodingviaContent-Type,suchasUTF-8,thoughHTML5'sisshorter.2.Itsupportspagerefreshorredirectionusingrefresh,likewaiting5s
    HTML Tutorial . Web Front-end 811 2025-07-12 01:26:22
  • PHP header already sent error
    PHP header already sent error
    The error "Cannotmodifyheaderinformation-headersalreadysent" appears because there is already content output before attempting to send HTTP header information in PHP. 1. Check whether there are spaces or content at the beginning of the PHP file and make sure
    PHP Tutorial . Backend Development 539 2025-07-12 01:25:30

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